The present invention relates in general to flow sensing apparata and in particular to such apparata which are cooperatively arranged with a coal processing plant cyclone in order to determine the presence of a flow stream from the cyclone outlet.
One very important stage in the mining and sorting of coal is the coal processing plant. As the coal is initially mined, pieces of rock become mixed with the coal and the mixture must be sorted. In certain instances, the coal is separated from the rock by means of a device called a cyclone. Any one coal processing plant may have a large number of such cyclones depending upon the volume of raw coal received. The type of cyclone employed in these processing plants operates as a separator between particles or pieces of one density (weight) and particles or pieces of a different density. By sorting the pieces according to size, density becomes the controlling factor of weight differential. The lighter pieces (coal) pass upwardly while the heavier pieces (rocks) pass downwardly. Consequently, it is important that the incoming mixture of coal and rock be crushed and sorted as to size before being introduced into a corresponding cyclone.
After the raw coal from the coal mine is crushed and then separated as to the size of rock and coal, several cyclones may be required to accommodate the various size groupings. Each coal and rock mixture is next mixed with water and directed into a corresponding cyclone under substantial pressure. While this slurry rotates around the body of the cyclone in a centrifugal manner, the heavier rock moves downwardly to an exit location and the lighter coal moves upwardly out of the top of the cyclone. The water and rock mixture exits the cyclone in a somewhat continuous flow manner and although this flow may be irregular in nature, it is critical to the operation of the cyclone that blockage of this cyclone outlet be identified at once. If blockage does occur, the operator must be able to tell so immediately in order to take the necessary precautionary steps and preclude rock and water from mixing with the pure coal that passes out the top of the cyclone.
At the present time, there is not believed to be any suitable means to sense when blockage occurs and to advise the operator of this fact. Consequently, in many present-day systems, rock will in fact mix with and thus pollute the otherwise relatively pure coal exiting from the top of the cyclone. If such polluting occurs for any length of time, the output product of the processing plant is substantially damaged. Although flow detection sensing systems are known to exist in the art as patented systems, none are specifically designed for sensing the outlet flow from a coal processing plant cyclone. Inasmuch as this particular type of flow stream sensing has a number of specific and unique requirements, any suitable flow sensing system must be specifically designed to accommodate these various uniquenesses. Listed below are potentially relevant references which offer some indication of the types of detection systems which have been conceived.
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 2,798,215 Domingo et al. 7/02/57 3,445,834 Street et al. 5/20/69 3,686,926 Miller et al. 8/29/72 3,878,103 Miller et al. 4/15/75 4,103,292 Haas 7/25/78 3,849,723 Allen 11/19/74 3,557,616 Landon, Jr. et al. 1/26/71 ______________________________________
Domingo et al. discloses a liquid detecting device which relies upon the electrical conductivity of the liquid for its operation. Two conducting rings, separated by insulating rings, are disposed in an outlet pipe and these two conducting rings are electrically coupled to a plug in jack which is cooperatively arranged with a temperature-time indicating mechanism.
Street et al. discloses a liquid monitoring apparatus for detecting the existence of a flowing liquid in a pipe, the apparatus having laterally spaced probes adapted for axial insertion into the pipe. One probe is disposed at a low level in the pipe, the other probe is central. Only when there is sufficient flow through the pipe is the distance of separation bridged by the flowing liquid and an indicating circuit activated.
Miller et al. ('926) discloses a chip detecting and monitoring device for detecting conductive and nonconductive material present in a fluid system line. A woven screen of parallel conductive wires and perpendicular nonconductive wires is electrically coupled to a battery source and light. When a condutive particle bridges to adjacent conducting wires, the light is illuminated.
Miller et al. ('103) discloses a metal chip detecting and monitoring device similar to the above-mentioned Miller et al. ('926) device. This particular reference is a continuation of a divisional of the earlier reference and thus provides no new subject matter.
Haas discloses a material sensing device for sensing the level or the flow of solids such as grain, gravel or crushed stone. The device includes a flexible hose secured within a junction box with a light-sensitive diode at one end of the hose and a light-emitting diode at the opposite end. A positive flexure of the hose as produced by material contact causes an attenuation that is able to be sensed.
Allen discloses a method and apparatus for measuring the electrolytic conductivity of the liquid wherein a dialectric sorption medium is employed to conduct the liquid from an accessible, exposed portion into operative contacting association between a pair of spaced contact electrodes.
Landon, Jr. et al. discloses a particle flow sensing device which includes piezoelectric means supported on and activated by an elongated member placed in the flow path of a particle-entrained flow. An electrical signal being produced in response to impact of the particles on the elongated member.
While these various disclosures may be considered as relevant to the present invention, the closest disclosure is believed to be that of the Landon, Jr. et al. reference. However, the Landon device involves a means to sense particle flow by radial compression of one side of a piezoelectric cylinder. The compressive force is caused by solid particles striking an elongated member extending across the majority of the diameter of the flow conduit. Although the Landon, Jr. et al. reference is believed to be the most relevant of those above-listed patent disclosures, the Landon, Jr. et al. device relies upon particle contact for mechanical sensing in lieu of electrical contact.
A further difference between the present invention and all of the above-listed references is that none of these references involve sensing of the flow exiting from a coal processing plant cyclone. While it may be argued that flow sensing is in fact only flow sensing and it makes little difference what the associated apparatus is, it should be understood that there are various aspects to coal process plant operation which establish certain requisites for any flow sensing apparatus. First, due to the fact that the processing plant operator is having to keep track of many operations at one time, his review of the operator control panel presents a myriad of lights, gauges and buttons and it would be an improvement to provide a flashing or flickering light as an indication of a properly flowing exit stream from each cyclone. Such a flickering or flashling light is an improvement visually to the operator and provides a type of dynamic indication of the nature of the exiting flow at any instant of time. A further benefit to be afforded the operator is a warning alarm sound such that when flow ceases for a predetermined interval of time, even though the light may be constantly on, the operator is able to hear the warning and know that flow has stopped and may then shut down the cyclone so as to prevent rock from backing up and polluting the exiting pure coal.
In addition to the above-listed patent references, another item of possibly relevant technology is known to exist, yet sufficient details are not known to be able to discuss all aspects. This other, possibly relevant technology pertains to the design and operation of a scanning system employed at one time by Krebs Engineers of Menlo Park, Calif. This scanning system used a switch assembly positioned to intersect the exiting flow stream from a cyclone, and the switch assembly used is a mercury switch (paddle-type). It is known that this system never performed satisfactorily, possibly because of the disadvantages provided by use of a mechanical switch.